Nut tap.



casing 8 is dropped over the ingot, the ingot, casing and all are raisedby the hoist 5, and the molten metal-ls permitted to solidify.

Forming the entire coating in bath 3 has the advantage of requiring onlyone bath of molten metal. However; it appears that after repeateddipping of iron ingots, segregating casings, etc. into baths ofsupermolten metal, the molten copper contains more iron thanbeforedoubtless the result of solution of the iron to a slight extent bythe molten copper. This tendency to dissolve the iron is greater, thehotter the molten metal; therefore when extreme purity of the coating isdesired, as when making coated ingots to be formed into electricalconductors, it is better to form the coating in two operations, themolten copper at ordinary casting temperature in bath 4 having little orno tendency to dissolve iron.

It is exceedingly important to prevent oxidation of" the molten metal,as it is very important that the quality of the metal of the coatingshall be good; and it is exceedingly difficult to keep copper and mostother metals in a molten condition, and particularly in a supermoltencondition, for along period of time, without serious absorption ofoxygen and other gases. I

'' therefore provide covers 19 for both baths which are removed onlywhen and so long as absolutely necessary, and I further cover thesurface of the molten metal so far as possible with powdered charcoal,providing a clear space for the passage of the ingot and easing by meansof a ring 20- of carborundum or other suitable refractory material whichfloats on the surface of the molten metaljring 2O confining the powderedchar- 1 further introduce into the molten metal, from such as a compoundof silicon with copper or other suitable metal; the silicon of suchcompound combining with the oxygen of any metallic oxids present or withthe oxygen of any or 00 contained inthe molten metal. Instead of fillingthe casing 8 from the bottom, as"

above described, I may cause it-to fill with molter'i metal introducednear the top of the casing. In such case I use a casing such as shown inFig. 3,having pouring holes 21 in its sides, and a. shield 22 normallycovering such openings. The bottom plate 12 having been applied to sucha casing, with the ingot 7 therein, and

the chamber being filled with a non-oxidizing atmosphere, as abovedescribed, the chamber is lowered into the molten metal until theopenings 21 are submerged; and shield 22 being then raised (or ifpreferred said shield may be raised just before openings 21 near thesurface of the molten metal) the molten metal flows through saidopenings 21 into the casing, displacing the non-oxidizing atmospheretherein and filling the space between the ingot and the sides of thecasing. This method of filling the casing avoids drawing of air into thecasing with theinflowing metal (as might be the case if molten metalwere poured through a.runner into openings 21 without submerging saidopenings in molten metal) and has the important advantage that the metalwhich fills the casing may be taken from the very best part of the metalin the bath.

The top layer of molten metal is apt to be poor, owing metal at thebottom of the bath is often badalso; but

' nickel, and cobalt.

.the metal intermediate these extremes will be good, if

proper care be observed, and if the casing be submerged until theopenings 21 are at the level .of the good metal, the formation of acoating of good quality is as sured. There being no air whatever in thecasing during the pouring in this manner, of course there can bepeculiarconstruction of bottom plate and lower end of casing} shown in Fig. 2,and by the use of proper packing material The V-section recess l5 at thelower edge of the casing and the V-section rib 14 of the bottom platecoact to center the casing accurately as it seats on the bottomplate;also since the packing ma terial inrecess 15 is in a recess, it is notwashed away by the molten metal as'the casing descends, but remains insaid recess until the rib 14, entering the recess,

squeezes out excess of packing material. The casing carries such amountof weight as is necessary to press it tightly against the bottom plateand insure a good joint. For packing material in recess 15 I commonlyuse asbestos cord or rope, 23, covered with a layer of graphite paste;24. To protect the casing and bottom I plate from the molten metal Ialso cover them with a layer of graphite wash.

To relievethe pressure on the joint between the easfrom the moltenmetal, I may apply vacuum to the casing through valve 10. Likewise, toprevent the forma tion of bubbles, blow-holes and the like in the metalcast as shown in Fig. 3, I may apply vacuum to the easing during orprior to the entry of the molten metal, whereby gas otherwise entrainedin the metal will be drawn off.

By the apparatus above described I can inseparably unite iron and steelwith such unlike metals as copper, silver, aluminium, gold, platinum,aluminium bronze,

By film-coating in the first instance with a metal which does notvolatilize before reaching the supermolten temperature required (forexample, byfilm-coating with supermolten copper or silver) I can alsounite iron and steel with brass and tin bronzes, the zinc or tin ofwhich volatilize or oxidize below'thesupermolten temperature required tounite them directly to the iron or steel. I can also unite inseparablynon-ferrous couples, of the above metals and similar metals, such ascopper and silver, for example.

It will be seen that the apparatus is particularly suitable for coatingwith easily-oxidizable metals, such as nickel, for the coating isentirely protected from contact with the air until cold.

By producer gas referred to above, I mean gas made from anthracite,coke, charcoal etc., and containing practically none of the hydrocarbonswhich tend to split or decompose; inother words, I mean an absolutelyfixed gas.

- ing and bottom plate while raising the filled casing PATENTED JULY 23,1907.

W. M. MCKENZIE.

NUT TAP.

APPLICATION FILED MAY 2a. 1906.

I [NVE/VTOR William if; f2 5977218.

Aliorney

